It is known to blend two or more polymeric materials to achieve beneficial performance characteristics in the resulting polymeric composition. One such conventional blending process is the blending of elastomeric and thermoplastic polymeric materials. For example, as described in U.S. Pat. No. 6,642,316, it is known to blend ethylene propylene based interpolymers with polypropylene so as to provide a polypropylene dispersed phase and an elastomeric continuous matrix phase. The overall blend may be elastomeric in nature. The ethylene propylene based interpolymers may be of the type described in WO 02/083754.
It is also known to blend an inverse distribution of phases, where the continuous matrix phase is a polypropylene and the dispersed is an ethylene propylene based interpolymer. The blends of this type are often referred to as TPO's (Thermoplastic Polyolefins). The dispersed phase acts as an impact modifier and improves the impact strength of the original polypropylene.
It is known to provide soft or softened resilient articles using styrenic block copolymers (“SBC's”). The SBC's may have a variety of hardness levels, expressed generally in Shore A. Generally elastomeric SBC's exhibit poor processability, limiting production capacity. For example, during continuous extrusion of SBC's for production of fibers or films, and the like, the extrudate may experience melt fracture, and therefore, may limit production line speeds.
WO 04/014998 discloses blends of polypropylene impact copolymers and SBC's. These blends also incorporate non-functionalized plasticizers.
U.S. Patent Application 2003/022975 discloses a blend of a highly crystalline isotactic polypropylene ethylene copolymer with a polyolefin elastomer, which may be a hydrogenated SBC. The compositions are described as having excellent rigidity and do not provide an elastic composition. U.S. Pat. No. 4,775,711 discloses elastomeric molding compositions that are blends of crystalline propylene-ethylene copolymers with block copolymers. EP 0 921 151 discloses compositions that are crosslinked blends of ethylene-alpha olefin copolymers and block copolymers. The blends are said to be useful for molding medical articles.
WO 2004/039907 discloses a hot melt adhesive incorporating up to 40 wt. % of a SBC, 4 wt. % to 50 wt. % of an RCP copolymer, and from 20 wt. % to 65 wt % of a tackifier. U.S. Patent Application 2002/0122953 discloses an elastic adhesive composition of a rubber-based adhesive, which may be a SBC and a semicrystalline polymer.
Other background references include U.S. Pat. No. 5,885,908, EP 0 241 667 A, EP 0 499 472 A, JP 2000 129027 A and JP 2004 338289 A.